Autonomic/Somatic nervous system Flashcards
Define:
Somatic
Afferent
Efferent
Ganglion
Autonomic nervous system
Viceral innervation
What is the somatic nervous system responsible for?
What relays the sensation from the skin and motor impulses to skeletal muscles?
- voluntary body movements + sensation of external stimuli
- 31 pairs of mixed spinal nerves
*NOTE: 8 cervical nerves despite only 7 cervical vertebrae
What is the autonomic nervous system for?
What are the 2 subdivisions and where are they?
- Exerts homeostatic control over visceral organs, smooth muscle and secretory glands
- Two functional divisions:
1. Sympathetic - Sympathetic chain – T1-L2/L3 lateral to the
vertebrae
2. Parasympathetic - Parasympathetic – located in the brain stem and sacral region (S2-S4)
What is the difference between somatic and autonomic efferent systems?
What is the difference between Parasympathetic and sympathetic efferent system?
Parasympathetic : Cranio-sacral nerves
* Long preganglionic neurons
* Shorter postganglionic neurons
* Preganglionic neurons synapse in ganglia close to the target organ
Sympathetic: Throaco-lumbar nerves
* Short preganglionic
* Long postganglionic
* Preganglionic fibres synapse further from target organ
Compare the effects of the SNS and PNS.
*Dont work exclusively… just favoured depending on context
Sympathetic: “fight or flight”
Parasympathetic: “rest and digest”
What is the heart insensitive to? Why is this?
-Cutting, touch, and temperature
>Doesn’t have somatic nerve supply
What happens during ischaemia/metabolite accumulation?
Why is pain referred to the image shown?
- Heart stimulates myocardial pain fibres (run with sympathetics)
-Somatic sensory fibres from these regions synapse in the same region as visceral sensory from the heart (T1-4/5)
-So interpretation from this pain arises from somatic region
What are the 2 main ANS control centres?
1: Brainstem
(medulla oblongata and pons)
* Cardiovascularcenters
(e.g. for blood pressure control)
* Respiratory centers
* Micturition
2: Hypothalamus
* Temperature
* Osmolarity
* Biologicalclocks
* Appetite
What are neurotransmitters?
What 2 neurotransmitters are important for ANS?
- Substance released by synaptic terminals for the purpose of transmitting information from one nerve cell to another
- Bind to postsynaptic membrane receptor where they have an effect
** Acetylcholine (ACh) * Noradrenaline (NA)
What neurotransmitter is related via pre ganglionic fibre AND post ganglionic fibre for:
-Parasympathetic NS
-Sympathetic NS
What are the 2 types of post-synaptic receptors?
How do they respond differently to neurotransmitter binding?
We have different receptor so organs can have different reactions to the same stimulus.
What are these?
- Cholinergic
* Synaptic transmission mediated by acetylcholine (ACh)
* Nicotinic
* Muscarinic - Adrenergic
* Synaptic transmission mediated by the release of noradrenaline (NA) or adrenaline
* Alpha (α) with subtypes α1 and α2
* Beta (β) with subtypes β1 and β2
- All pre-ganglionic neurons of the ANS are…
How do preganglionic neurones communicate with the post synaptic membranes? - Are the ganglioic posynaptic receptors ionotropic or metabotropic ?
-Cholinergic : they release ACH.
-Ionotropic
Post-ganglionic neurons of the ANS are…
Post-ganglionic post-synaptic receptors are ….
-Metabotropic
When it comes to Eccrine sweat glands the sympathetic nervous system releases what neurotransmitter from its post ganglionic neurone? i.e how is this different.
-ACH
How does adrenal medulla work?
Look at the overview fill in the gaps.
The ANS in action:
-Control of bronchial smooth muscle (1)
What causes contraction of bronchial smooth muscle?
-Increase phosphorylation of myosin heads = contraction of smooth muscle +Vice versa
- Regulated by 2 Enzymes:
>Increase MLCK = increase phosphorylation
>Increase MLCP = decrease phosphorylation
The ANS in action:
-Control of bronchial smooth muscle (2)
How is adrenaline key mediator in the sympathetic signalling on bronchiole smooth muscle?
1) Adrenaline related by adrenal glands via Sympathetic NS
2) Bronchiole smooth muscle membrane has B2-AR activated by adrenaline
3) B2-AR are Gs linked protein coupled receptors - metabotropic
4) Adrenaline binds > Gs dissociates from receptor > activates AC >catalyses ATP to cAMP > actives PKA > phosphorylates MLCK > inactivates MLCK > less phosphorylation of myosin heads > smooth muscle relaxation
-Increased sympathetic activity leads to bronchodilation
The ANS in action:
-Control of bronchial smooth muscle (3)
How is ACH key mediator in the parasympathetic signalling on bronchiole smooth muscle?
1) Postganglionic parasympathetic fibres release ACH > activate M3-AchR (muscarinic ACH receptor) on the membrane of bronchiole smooth muscle cell
2) M3-AchR are Gq linked metabotropic receptors
3) ACH binds Gq dissociates from receptor and activates PLC > liberates IP3 + DAG from PIP2.
4) IP3 binds and opens IP3 receptors on surface Sarcoplasmic reticulum > releases Ca2+ from SR increase in cytosolic Ca2+
5) Ca2+ binds and activates enzyme CaM (calmodulin) > activates MLCK > increases phosphorylation of myosin heads > contraction of bronchiole smooth muscle.
The ANS in action:
Sweat glands (1)
Where are sweat glands found and what are they innervated by?
-Dermis
-Postganglionic sympathetic fibres NOT parasympathetic fibres > only under sympathetic control.
The ANS in action:
Sweat glands (2)
1) Sympathetic fibres enervating sweat glands are cholinergic
2) Sweat glands express M3-AchR which are Gq linked
3) ACH released from post ganglionic sympathetic neurone binds to receptor and Gq subunit dissociates from receptor and activates membrane bound PLC.
4) Splits PIP2 into IP3 + DAG
5) IP3 binds to and opens IP3R on surface endoplasmic reticulum > Ca2+ release and increase in cytosolic Ca2+ conc
6) DAG activates PKC
7) Second messengers lead to chloride efflux in lumen of sweat gland
8) Series of ion fluxes leads to sweat production
